Particle mixing, granulating and sizing operations are widely employed in numerous industrial fields, such as in the pharmaceutical and food industries. The control of particle size is an important unit operation for improving particle handling, particle quality, fluidization during fluidized drying, etc.
Thus far, conventional particle crushing and sizing apparatuses regulate particle size using screens. Herein, screens wear off and break down as a result of continued use. Also, worn off powder or broken chips from the screens may contaminate the product particles. In order to avert the above, a strict quality control management is required involving frequent screen checks.
These apparatuses have also problems in that, in the case of wet materials, the screen mesh can become clogged with the processed material, depending on its nature, as it becomes undesirably kneaded in the screen. Also, the impact force of the granulating blades may crush particle having the right size, resulting in an excess of fine powder and thus lower yields.
Therefore, the inventors of the present application developed a particle crushing and sizing apparatus using no screens (Japanese Unexamined Patent Application Publication No. 2000-117131).
The particle crushing and sizing apparatus disclosed in Japanese Unexamined Patent Application Publication No. 2000-117131 is a particle crushing and sizing apparatus for sizing, through a predetermined holding region, wet or dry material granulated or formed by various devices and supplied from a material input port, the apparatus comprising a casing, a rotation body, an opposed face portion opposed to the rotation body at a predetermined distance, and a gap region defined by the rotation body and the opposed face portion which are provided within the casing, the gap region comprising a particle size adjusting region which allows particles suited to the gap setting to pass but does not allow particles not suited to the gap setting to pass, wherein the particles not allowed to pass through the gap region are brought into contact with the opposed face portion in association with rotation of the rotation body at an inlet or face sections of the gap region and are crushed to such an extent that the particles can pass through the gap region and discharged from a discharge port.
Herein, the gap region is composed of the face or the line sections for setting the space between the rotation body and the opposed face portion as the narrowest gap, and the particles are crushed in the narrowest gap or in the vicinity thereof.
Specifically, the rotation body is formed into a substantially conical shape, the casing is formed into a substantially hollow conical shape, the particle holding region is constituted by a casing inner wall and the rotation body, and the narrowest gap is constituted by the lower end peripheral edge of the rotation body and the inner wall of the casing.
However, in the particle crushing and sizing apparatus with the above constitution, the narrowest gap formed by the lower end peripheral edge of the rotation body, formed into a substantially conical shape, and the inner wall of the casing, formed into a substantially hollow conical shape, has a linear shape in the form of a circumference, for which reason the crushing and sizing range is relatively restricted.
Enlarging the lower diameter of the rotating body can broaden the above crushing and sizing range, but at the cost of a larger apparatus size.
Thus, an object of the present invention is to provide a particle crushing and sizing apparatus having a sufficiently large crushing and sizing range.